1. Field of the Invention
The present invention relates to a stage system with onboard linear motor to provide a position controller energized with a linear motor, which has been extensively used in fields as diverse as semiconductor industries, industrial robots, inspection equipments, machine tools, and so on.
2. Description of the Prior Art
A slider unit with onboard linear motor made compact or slim in construction is disclosed in Japanese Patent Laid-Open No. 266659/1997, in which a small linear-motor table system is made to propel any one of confronting bed and table relatively to another. A solenoid-energized linear actuator is installed between the bed and the table, at least any one of which serves for a yoke of the solenoid-energized linear actuator, thus allowing the linear-motor table system to be made slim in size and in expensive in production cost.
Disclosed in Japanese Patent Laid-Open No. 266660/1997 is an X-Y table system that adopts a solenoid-energized linear actuator to be made compact or slim in construction. With the X-Y table cited earlier, all of a power line for the solenoid-energized linear actuator and wires for taking out signals from various sensors are held together on an intermediate moving member of X-table and assembled into a single cord that will be connected to any outside control unit. This arrangement helps lessen any potential negative affection that might be otherwise caused by the wires and realize well the high speed, durability, less occurrence of debris and overall shrinkage in size.
Moreover, a slider unit constructed as illustrated in FIG. 12 has already been developed and disclosed in the co-pending senior application that was opened under Japanese Patent Laid-Open No. 352744/2001. The slider unit has an onboard moving-magnet linear motor and is envisaged improving high-speed operation and much response ability of the movable table 60 relatively to the stationary bed 64 and also realizing much more accurate position control of the table 60 to the bed 64. With the slider unit, the three-phase conduction system is adopted for conduction to any armature winding 65 while the driving circuit is removed to any outside driver. This design can provide the bed 64 that is made simple in construction and also reduced in height. The stationary bed 64 in the slider unit is made of magnetic material while the movable table 60 is also made of magnetic material and arranged for sliding movement with respect to the bed 64 through a linear motion guide unit 61 that is mainly comprised of a slider 62 and a track rail 63. The movable table 60 has mounted thereon with a field magnet 66 on which magnetic poles are arranged in such a way that they alternate in polarity along a traveling direction of the table 60, while the bed 64 has the armature windings 65 on a surface of the bed 64, which is in opposition to the field magnet 66. In addition, there is provided a position detector composed of a linear scale 68 and a sensor 67 to determine the position of the table 60 with respect to the bed 64 in the traveling direction of the table 60.
Moreover referring to FIG. 13, there is shown a prior rotary table system in which a servo-actuator is connected directly to a motor 81 in direct-drive manner to accomplish the very fast, highly accurate position control in turning direction with no backlash or no lost motion. The servo-actuator to control an angular position of a table 70 with high speed is mainly comprised of the motor 81, an optical encoder 78 and a rolling-contact bearing 72. The motor 81 is comprised of a rotor core 77 fixed to the table 70, and a stator core 76 mounted on a housing 71. With the rotary table system stated earlier, the table 70 is encased in the housing 71 for free rotation through the rolling-contact bearing 72 that is composed of an inner ring 74, an outer ring 73 and rollers 76. The rolling-contact bearing 72 is constructed with a crossed-roller bearing in which the rollers 75 are arranged circumferentially with their axes intersecting alternately one another in such a manner that each roller can carry the table 70 against any load in every direction, either radial or axial.
By the way, the table-position control system or the stage system used commonly for various machines such as semiconductor fabricating equipments is to move the work such as a semiconductor stock and the like, which is mounted on the movable table, in any one or both of X-direction and Y-direction perpendicular to the X-direction, and/or turn the work over an angle xcex8 thereby transferring the work to any desired position. To keep the workroom environment clean, the linear motors have been extensively employed for the driving means to move the table or the stage, whether linear or angular. Recently the systems that are used to manufacture the semiconductors are legion, and the semiconductor industries, image processors, inspection instruments or the like further need the position controls of high accuracy, even with compactness and inexpensiveness.
With the rotary table system as shown in FIG. 13, nevertheless, the rotor core 77 of the motor 81 is arranged overall around the periphery of the table 70 while the stator core 76 is installed circumferentially in an annular groove in the housing 71 in opposition to the rotor core 77. This type of the prior rotary table system results in becoming tall in height and a corresponding increase in dimensions, and also would get complicated in construction itself. The prior stage system as stated earlier and shown in FIG. 12 uses the linear motor, but only to propel the table in linear direction through the linear motion guide unit, not to provide position controls in a circular or angular direction. Thus, it remains a major challenge to provide a stage system that will be allowed to not only travel in linear direction, but also provide accurate position control in circular direction or in angular xcex8 direction by the use of some linear motors, which are substantially identical to one another in construction to reduce the desired parts and members making up the stage system in their numbers, thereby helping make the stage system smaller in dimensions, lighter in weight, even with better in response ability than the same sort of prior table system ever developed.
It is the primary object of the present invention to overcome the major problem as described just above and to provide a stage system with onboard linear motor, which is constructed to allow position control of tiny angles in either direction of turning or in xcex8 direction. Still more particular object of the present invention is to provide a stage system with onboard linear motor, which may afford a moving table high-precision angular-position control and better response ability, even being made thin and small in dimensions, light in weight and compact or slim in construction.
The present invention is concerned with a stage system with onboard linear motor, comprising an anti-turning stage kept against rotation, a turning stage lying on the anti-turning stage for rotation relatively to the anti-turning stage, a rolling bearing means interposed between the anti-turning stage and the turning stage to support the turning stage for free rotation, and a turning linear motor for driving the turning stage over a tiny amount of angle in either direction of rotation, wherein the turning linear motor is comprised of a primary side of more than one armature winding arranged in juxtaposition in straight line on either one of the turning stage and the anti-turning stage, and a secondary side of field magnets arranged in juxtaposition in opposition to the armature winding on another of the turning stage and the anti-turning stage, with magnetic poles alternating in polarity in straight line.
In an aspect of the present invention, there is provided a stage system with onboard linear motor, in which the turning linear motor is oriented so as to extend in line with a tangent of an arc depicted by the turning stage. In another aspect of the present invention, moreover, a stage system with onboard linear motor is provided in which the turning linear motor has a means for sensing a position of the turning stage in turning direction with respect to the anti-turning stage, the sensing means being composed of a linear scale graduated lengthwise in fine pitches and attached on the arched periphery of the turning stage, and a sensor element installed in opposition to the linear scale to read graduations on the linear scale. In another aspect of the present invention, moreover, a stage system with onboard linear motor is provided in which the rolling bearing means is constituted with a cross-roller bearing that is composed of an inner ring, an outer ring arranged around the inner ring for rotation with respect to the inner ring, and roller interposed between the inner ring and outer ring, with their rolling axes being crossed alternately one another.
In a further another aspect of the present invention, there is provided a stage system with onboard linear motor, in which the anti-turning stage is made at central area thereof with an aperture in which the outer ring of the rolling bearing means is fitted, while the turning stage is provided with an annular boss having an outside periphery around which the inner ring of the rolling bearing means fits over the annular boss, and the turning stage is also made at a center thereof with a rectangular window that is in alignment with the aperture in the anti-turning stage. In another aspect of the present invention there is provided a stage system with onboard linear motor, in which the anti-turning stage is composed of a first stage lying on a base stage for linear movement in an X-direction relatively to the base stage, and a second stage lying on the first stage for linear movement relatively to the first stage in a Y-direction crossing the X-direction, and the turning stage lies on the second stage to be supported through the rolling bearing means on the second stage. In a further aspect of the present invention, moreover, a stage system with onboard linear motor is provided in which a first linear motor is provided to move the first stage to a desired position in the X-direction, and a second linear motor is provided to move the second stage to a desired position in the Y-direction.
In another aspect of the present invention there is provided a stage system with onboard linear motor, in which the turning, first and second linear motors equally have one set of three armature windings, each of which carries any one phase of three-phase conduction system, and the first, second and turning stages are each propelled to their desired positions by virtue of electromagnetic force that will be generated when three-phase current in the armature windings interacts electromagnetically with field flux created by the field magnets. In another aspect of the present invention, moreover, a stage system with onboard linear motor is provided in which the field magnets are made of rare-earth magnet and five pieces of field magnets are arrayed in straight line in opposition to each set of three armature windings.
In another aspect of the present invention there is provided a stage system with onboard linear motor, in which linear movement of the first stage in the X-direction relatively to the base stage is guided through a first linear motion guide unit that is composed of an elongated track rail lying on the base stage in the X-direction and a first slider mounted to the first stage and supported on the track rail for linear movement, while linear movement of the second stage in the Y-direction relatively to the first stage is guided through a second linear motion guide unit that is composed of a second track rail lying on the first stage in the Y-direction and a second slider mounted to the second stage and supported on the track rail for linear movement. In a further another aspect of the present invention, a stage system with onboard linear motor is provided in which the first, second, and turning stages are equally made with transparent windows, which parallel each other.
In another aspect of the present invention there is provided a stage system with onboard linear motor, in which first sensing means for determining a relative position of the first stage to the base stage is constituted with an optical encoder that is made up of an optical linear scale attached to the first stage and a sensor element mounted to the base stage in opposition to the optical linear scale, while second sensing means for determining a relative position of the second stage to the first stage is another optical encoder made up of an optical linear scale installed on the second stage and a sensor element mounted to the first stage in opposition to the optical linear scale. In another aspect of the present invention, moreover, a stage system with onboard linear motor is provided in which all the first, second and turning stages are made in a form of rectangular plate.
With the stage system of the present invention constructed as stated earlier, the turning linear motor is especially made up of the primary side of some armature windings arrayed in juxtaposition in straight line on either one of the turning stage and the anti-turning stage, and the secondary side of field magnets arranged in juxtaposition in opposition to the armature windings on another of the turning stage and the anti-turning stage, with magnetic poles alternating in polarity in straight line. This construction of the turning linear motor is good enough in operation to provide angular position control over a tiny amount of turning of the turning stage, with even keeping the stage system simple in construction. In addition, the construction in which the turning part is constituted with the field magnets of permanent magnet contributes to reducing the turning part itself in weight, improving the response ability in turning motion of the turning part with even less overall thickness, making certain fewer occurrences of debris that might be caused by the stage system itself, and also making the system small in overall size.
In accordance with the stage system of the present invention constructed as described above, the linear motor that has been predominantly used for position control in any linear direction is adopted just as it is to provide angular position control over tiny angle of turning. This concept realizes the stage system that allows high-precision position control of tiny angle of turning and high response ability in position control, with even small in size, simple in construction and weighing less. Linear position control in either direction of X- and Y-directions is done by other linear motors to move the anti-turning composite stage of an X-stage and a Y-stage kept against turning. With the stage system of the present invention stated earlier, standardized armature windings and field magnets are interchangeable to yield all of the turning linear motor to force the turning stage in circular direction and other linear motors to move the composite stage in linear direction, with simply requiring any modification in mounting of the linear scale. This results in a reduction in a number of parts and components as well as in production costs compared with the conventional systems. This stage system of the present invention is available well for various machines such as semiconductor manufacturing equipments, industrial robots, inspection instruments, machine tools and so on.